Sheviis, Chapter Two, Mishnah 10.
"HaDelu'in shekiyeman lezera" - gourds that a person left over for their seed, meaning that they grew to full size and were left attached to the ground in order to obtain seed from them, right before the Shemittah year.
"Im hikshu lifnei Rosh HaShanah venifselu me'ochel adam" - if they hardened before Rosh HaShanah and thereby became unfit for human consumption already before Rosh HaShanah, then "mutar lekayeman ba'sheviis" - it is permitted to leave them in the ground during Sheviis for the sake of the seed and to make use of the seed, because they are completely sixth year produce and not produce of Sheviis.
"Ve'im lav" - if they did not harden completely, they are still fit to be eaten and are still growing, and therefore "asur lekayeman ba'sheviis" - they may not be left standing during Sheviis after the time of biur.
The Gemara explains how one checks whether they hardened or not: a needle is stuck into the gourd. If the hole closes up, that is a sign that it is still moist; and if the hole remains open, that is a sign that it has hardened completely.
"Veha'temaros shelahen asuros ba'sheviis":
The "temaros" of the gourds are either tiny buds that look like dates, or alternatively small branches. They are considered part of the growth of the gourd, and therefore they carry the sanctity of Sheviis just like any other part of the gourd.
"U'marbitzin be'afar lavan, divrei Rabbi Shimon":
Another activity that is permitted during Shemittah is watering a field, which is called "marbitzin be'afar lavan", and this is the opinion of Rabbi Shimon. The Rambam explains that Rabbi Shimon is referring to a field full of trees, one that has at least ten trees spread out within a beis se'ah, and in his opinion it is permitted to water it in order to preserve the trees so that they will not be ruined during Shemittah. The Rambam adds that if the trees are more densely planted, not only Rabbi Shimon but everyone agrees that watering is permitted and is not considered a forbidden activity. However, "Rabbi Eliezer ben Yaakov oser" - he forbids it, unlike Rabbi Shimon.
"Memarsin ba'orez ba'sheviis":
Rice grows in a flooded field and requires a large amount of water, and it is permitted to water it during Shemittah - provided that it took root before Rosh HaShanah of the Shemittah year. As we learned earlier, the year to which a crop belongs is determined by when it takes root; and since the rice took root before Shemittah, it is not considered part of Shemittah, and therefore it is permitted to water it.
"Rabbi Shimon omer" - there is one activity involving rice that may not be done: they would cut off the leaves of the rice plant in order to benefit it, and in Rabbi Shimon's opinion this activity may no longer be done during Shemittah.
In summary: in this Mishnah we learned the law of gourds that were left for seed - that if they hardened and became unfit for human consumption before Rosh HaShanah it is permitted to leave them standing during Sheviis, and if not it is forbidden to leave them standing after the time of biur; the law of the temaros, which carry the sanctity of Sheviis; the dispute between Rabbi Shimon and Rabbi Eliezer ben Yaakov regarding watering a white field; and the permission to water rice that took root before Rosh HaShanah, alongside the opinion of Rabbi Shimon who forbids cutting off its leaves during Sheviis.